The asymmetry of tidal waves in estuarine areas has a significant amplifying effect on storm surges. An analysis of tidal wave asymmetry and its spatial distribution in the Yangtze Estuary was conducted using long-term tidal level data. Furthermore, extensive numerical simulations were performed using FVCOM to investigate the responses of estuarine surges to tidal wave asymmetry under different tidal ranges and tidal timing scenarios. The results indicate that tidal wave asymmetry in the Yangtze Estuary exhibits a spatial pattern of intensification upstream, with local topographic variations being the direct cause of increased tidal wave deformation. Specifically, under the same water level conditions, surges are markedly greater when a typhoon coincides with the flood tide than with the ebb tide. This is mainly because the surge-tide interaction accelerates tidal wave propagation, intensifies tidal wave asymmetry in the estuary, steepens the flood tide curve, and increases surge sensitivity to phase shifts. In estuarine areas with pronounced tidal asymmetry, the skew surge is a more suitable indicator for describing the capacity of typhoons to elevate hazardous tidal levels.
